Photosynthesis and the Environment

1
Photosynthesis and the Environment
6 CO2 (g) 6 H2O(l) ? CH2O 6 O2(g)
Net CO2 uptake photosynthetic CO2 uptake
photorespiratory CO2 evolution
respiratory CO2 evolution
Net O2 evolution photosynthetic O2 evolution
photorespiratory O2 uptake
respiratory O2 uptake
2
Light Intensity and the Rate of Photosynthesis

• Irradiance light intensity per unit area of
  leaf
• Light response curve shows the effect of
  increasing irradiance on the rate of
  photosynthesis
• Light-compensation point - CO2 uptake equals CO2
  evolution
• Light-saturation point occurs at the irradiance
  level at which the carbon fixation reactions
  reach a maximum overall rate

3
Temperature and the Rate of Photosynthesis

• The light reactions are not affected by
  temperature
• Calvin cycle is affected because of enzymes
• Optimal temperature is between 10OC 30OC
• Above 40OC enzymes may become denatured

Influence of some factors on the rate of
photosynthesis
4
Oxygen Concentration and the Rate of
Photosynthesis

• High oxygen levels have an inhibitory effect on
  photosynthesis
• Competition between O2 and CO2 for the active
  sites on rubisco

5
Photosynthetic Efficiency

• Quantum yield net CO2 uptake per unit of light
  energy (photons) absorbed
• C3 plants are more efficient at lower
  temperatures and C4 plants are more efficient at
  higher temperatures

6
Sun Plants vs. Shade Plants

• Shade plants have thinner, broader and greener
  leaves
• Shade plants more efficient at harvesting light
  at low intensities
• Sun plants have a higher light-compensation point
• Sun plants have a higher light-saturation point

7
Cheaper New More Effective Solar Cells Imitate
Photosynthesis - They employ synthetic pigments
imitating the natural ones - Softpedia